1. Field of the Invention
The present invention relates to a data recording and reproducing device, a data recording and reproducing method, and a camera device, in which whether or not to attenuate light from a light emitting element within its emission path is switched between when reproducing data and when recording data, or in accordance with the kind of an optical disc.
2. Description of the Related Art
As an example of an optical recording medium onto or from which data is recorded or reproduced by light, for example, a disc-shaped optical disc is widely used.
In a data recording and reproducing device for an optical disc, in a state with the optical disc rotated at high speed, light is generated by a light emitting element within an optical pickup, and this light is radiated from the optical pickup onto the optical disc as a light beam, thereby executing a data recording and reproducing operation. At this time, by performing focus control and tracking control accurately with respect to the optical pickup, the light beam from the optical pickup is accurately radiated to the track in the signal recording surface of the optical disc.
In the related art, there is an optical recording and reproducing device in which light from a light emitting element is attenuated in a path within an optical pickup by light attenuating means at the time of data reproduction, and the light attenuating section is retracted from the path at the time of data recording (see, for example, Japanese Unexamined Patent Application Publication No. 6-131638).
According to Japanese Unexamined Patent Application Publication No. 6-131638 mentioned above, an ND (neutral density) filter is suitably used as the light attenuating means. As the means for driving the ND filter, an ND filter driving section that moves the ND filter into and out of the above-mentioned optical path is disclosed.
The reason for inserting the ND filter into the above-mentioned optical path in Japanese Unexamined Patent Application Publication No. 6-131638 is, in a word, to reduce reproduction noise.
More specifically, in the case of an optical recording and reproducing device, it is necessary to set the optical power density at the recording surface higher at the time of recording than at the time of reproduction. Thus, a high-output laser diode (LD) is generally used as the light emitting element. In the case of a high-output LD, the light quantity does not becomes stable if the laser emission power is set low at the time of reproduction, and this is likely to cause a reduction in C/N (Carrier to Noise ratio) at reproduction. Accordingly, at the time of reproduction, it is necessary to make the laser emission power somewhat large while lowering the optical power density at the recording surface to a predetermined constant value.
These two mutually contradictory demands can be met by inserting the ND filter into the optical path at the time of reproduction.